Fastening systems of various types have long been known in the art. One common type of fastening system is the adhesive fastening system. Adhesive fastening systems have long been used on disposable absorbent articles, such as diapers and sanitary napkins.
Adhesive fastening systems, such as tape tabs, are used on diapers to secure such absorbent articles about the waist and torso of the wearer. The diaper may be removed for inspection of the wearer and to be discarded when soiled. Examples of attempts in the art to make adhesive fastening systems for disposable diapers are illustrated by commonly assigned U.S. Pat. No. 3,848,594 issued Nov. 19, 1974 to Buell; U.S. Pat. No. 4,699,622 issued Oct. 13, 1987 to Toussant et al.; and European Patent Application 0,233,704A2 published Aug. 26, 1987 to Buell.
In sanitary napkins, adhesive is used to temporarily and detachably join the garment facing surface of the sanitary napkin to the undergarment of the wearer. Sanitary napkins, like diapers, comprise a liquid pervious topsheet, which faces and contacts the skin of the wearer, a liquid impervious backsheet which is opposed to the topsheet, and an absorbent core intermediate the topsheet and the backsheet. The backsheet has a garment facing surface which is oriented towards and contacts the undergarment of the wearer and a surface opposed thereto which is oriented towards the core. When the sanitary napkin is soiled it is detached from the undergarment of the wearer. A new sanitary napkin is installed and adhesively joined to the undergarment. An example of such adhesive in a sanitary napkin is illustrated by International Patent Publication WO 92/04000 published Mar. 19, 1992 to Papa et al.
One improvement to the fastening systems of such disposable absorbent articles is the use of mechanical fastening systems comprising hook and loop type fastening members. Typically such fastening systems involved two major components, a prong which is joined to and extends outwardly from a substrate. The mechanical fastening system engages a complementary second component, a receiving surface. The receiving surface typically comprises one or more layers of strands or fibers.
A projection of the prong of the fastening system, typically referred to as the "engaging means" penetrates the receiving surface and engages or intercepts strands or fibers of the receiving surface. The resulting mechanical interference and physical obstruction prevent removal of the prong from the receiving surface until separation forces exceed either the peel strength or the shear strength of the fastening system.
Such mechanical fastening systems have been suggested in the art to augment or replace adhesive fastening systems. Mechanical fastening systems used in disposable absorbent articles provide the advantage that the adhesive does not become blocked, and hence inoperable or ineffective, with multiple inspections of the disposable absorbent article or become contaminated by oil from the fingertips of the inspector. Examples of mechanical fastening systems in a disposable diaper are illustrated by commonly assigned U.S. Pat. No. 4,846,815 issued Jul. 11, 1989 to Scripps; U.S. Pat. No. 4,869,724 issued Sep. 26, 1989 to Scripps; and U.S. Pat. No. 4,963,140 issued Oct. 16, 1990 to Robertson et al.
However, to date, the advances and use of such mechanical fastening systems in the art have focused principally upon the prong, such as making it more "skin friendly" (less abrasive) to the wearer, providing a disposal means for the garment when it is soiled, etc. However, little attention has been paid in the art to the substrate to which the prongs of the mechanical fastening system are joined.
The substrates are typically films, such as polyolefins, and are inelastic. However, inelastic substrates provide several disadvantages vis-a-vis elastic substrates when used for the fastening system in a disposable absorbent article. For example, an elastic substrate in a mechanical fastening system used in a disposable absorbent article eliminates, or at least reduces, the size of the elastic waistband. If the substrate of the fastening system can yield, much smaller elastic components can be utilized in the diaper to achieve expansion and fit around the stomach of the wearer. Furthermore, if the fastening system can yield under the stresses of application to the wearer and subsequent wearing, the forces and associated strains can be accommodated by the mechanical fastening system. Accordingly, the remaining materials of the diaper do not have to be as strong, because the stress is not localized at a rigid fastening member. Additionally, a rigid fastening material imparts a dead zone at the point of attachment. This dead zone causes a loss of extension on an elastically extensible waist margin of the diaper and may have a deleterious effect on the fit of the diaper to the wearer. Finally, an extensible substrate for the mechanical fastening system provides more versatility in the design of the diaper. The receiving surface for a fastening system having an extensible substrate can be placed anywhere on the diaper. It is not necessary that the receiving surface be coordinated and juxtaposed with an elastic waistband or other features of the diaper.
Moreover, an extensible substrate provides benefits which extend beyond disposable absorbent articles and which can be more generally applied and appreciated. For example, each prong of a mechanical fastening system having an extensible substrate can operate more independently of the other prongs, due to the inter-prong strain which can be accommodated. Such accommodation prophetically provides greater peel strength and greater shear strength than a fastening system having an inelastic substrate, because more prongs remain engaged on a fastening system having an elastic substrate. Furthermore, the extensible substrate allows for expansion and deformation of the object secured by the mechanical fastening system without exerting undue stresses on the object.